In a distributed storage system, network storage accessible to a network client is distributed over a plurality of network storage servers. Typically a nested multilayer directory structure keeps track of the respective network storage server that stores each directory or file in the distributed storage system. It is well known to display to a network client a portion of such a nested multilayer directory structure of directories and files accessible to the client. Various details of the directory structure can be accessible to the operating system of the network storage server but hidden from the network clients. Examples of such directory structures are found in Uday Gupta U.S. Pat. No. 6,775,679 issued Aug. 10, 2004, incorporated herein by reference, and Venkatesh et al. U.S. Patent Application Publication No. US 2003/0158836 published Aug. 21, 2003, incorporated herein by reference.
In some distributed storage systems, a single, centralized metadata server is accessed to search or update the nested multilayer directory structure. Such a centralized metadata server, however, becomes a bottleneck to file access and a single point of failure.
In the absence of a centralized metadata server, the directory search and update function are distributed among multiple servers. In this case, different portions of the directory structure are stored in different servers, and the directory structure provides links between the different portions. For example, each of the different portions of the directory structure is a respective Unix-based file system in one of the servers, and the links correspond to mount points in the nested multilayer directory structure.